1. Field of the Invention
This invention relates to the art of repairing heat exchangers and more particularly to an explosive tube plug adapted to effectively seal defective heat exchanger tubes.
2. Description of the Prior Art
It has been determined that over the extended lifetime of a heat exchanger, a small number of heat exchanger tubes may develop cracks and leaks. Since it is undesirable to allow the normally separated fluids coursing through the exchanger from coming into direct contact with other, numerous techniques have been developed to seal the leaking tubes.
For example, these defective tubes may be sealed by employing welded plugs, explosively expanded plugs or mechanically driven plugs. Unfortunately, however, these methods present difficulties which may detract from their effectiveness.
Welded tube plugs require direct access to the tube sheets disposed within the exchanger. Often times such access may prove to be quite difficult. Generally, a solid plug is inserted into each end of the defective tube. A weld bead is then deposited about the circumference of the tube plug to insure a pressure tight seal between the plug and the tube wall. Unfortunately, it has been learned through experience that fluid may penetrate the tube-plug interface and corrode the weld bead thereby causing leakage and rendering the whole procedure useless.
Mechanically driven plugs are difficult to install consistently.
The explosive plugs presently in use form a metallurgical bond between the tube and the plug. Unfortunately, it is feared that the relatively uncontrolled explosive force necessary for this procedure may distort the thin ligaments located between adjacent tubes in the tube sheets.